The present invention relates to a screen printing apparatus and a screen printing method for printing on a board using cream solder.
To secure good print quality in screen printing that prints on a board using cream solder, it is necessary to properly set, in accordance with a subject of printing, print parameters that determine various printing conditions. For example, it is necessary to set, in accordance with the characteristics of a print subject, various parameters such as the squeegee moving speed (i.e., the speed at which a squeegee is moved slidingly on a screen mask) and the printing pressure at which the squeegee is pressed against the screen mask.
A method that is commonly employed to make the print parameter setting as easy as possible is such that a print parameter library of standard sets of print parameters for plural kinds of solder are prepared in advance (refer to patent document 1, for example). With such a print parameter library, a standard set of parameters can be used for an existing solder type and hence the load of condition determining work for parameter setting that requires a high level of skill can greatly be reduced.
In many cases, it is possible to accommodate a new solder type by using existing print parameters with fine adjustments made to part of them and correcting the existing print parameters in accordance with print results, if a similar solder type is available. As the number of registered solder types increases, the contents of a print parameter library expand and the print parameter setting work is made more easier.
[Patent document 1] JP-A-10-146953
However, in recent years, because of the requirement from the environmental protection, new solder types such as lead-free ones have come to be used that are much different in composition from conventional lead-tin-based solder types that have been used commonly. Such new solder types are narrow in the range of applicability with electronic components and boards and hence are low in multiplicity of use: in an electronic components mounting line, it is necessary to selectively use many kinds of solder for various board and component types. There frequently occur cases that a conventional print parameter library cannot be used (even with modifications). A manufacturer may be obliged to do condition determining work on a trial-and-error basis to set print parameters, in which case print parameters may not be set quickly or properly.